Lecture 2: Odontogenesis

Question 1

teeth arise from what germ layer?

Answer 1

ectoderm

Question 2

odontogenesis begins in what week?

Answer 2

6th

Question 3

what, in chronological order, are the 4 epithelial stages of teeth formation?

Answer 3

• epithelial dental lamina stage (6th week)
• epithelial bud stage
• epithelial cap stage
• epithelial bell stage (enamel organ)(four layers)

Question 4

what are the three parts of the tooth germ

Answer 4

• enamel bell/organ (epithelium)
• dental papilla (mesenchyme)
• dental follicle (mesenchyme)

Question 5

cells arising from the dental laminae (primary and secondary) become the odontogenic ___ part of the a tooth germ

Answer 5

epithelial

Question 6

the epithelial bud cells are continuous with the cells of what?

Answer 6

primary dental lamina

Question 7

concerning primary buds, what is the timeline for central incisors and second molars?

Answer 7

central incisors= 6 weeks in utero

second molars= 8 weeks in utero

Question 8

concerning permanent buds, what is the timeline for first molars, central incisors, second molars, and third molars

Answer 8

first molar= 4 months in utero
central incisor= 5 months in utero
second molar= 10 months postnatally
third molar= 5 years postnatally

Question 9

concerning the cap stage, what is the concentration of epithelial cells that is a signaling center which determines if the tooth will develop to become an anterior or posterior tooth

Answer 9

enamel knot

Question 10

from inner to outer, what are the four layers of the enamel organ/bell stage?

Answer 10

• inner epithelium
• stratum intermedium epithelial layer
• stellate reticulum epithelial layer
• outer epithelial layer

Question 11

secondary dental lamina is facial/lingual to the primary

Answer 11

lingual

Question 12

secondary dental lamina arises from where?

Answer 12

primary dental lamina (not oral epithelium)

Question 13

what is the only part of the tooth germ that is avascular?

Answer 13

enamel organ

Question 14

after the formation of enamel is complete, the ameloblasts, along with the other layers of the enamel organ come together over the surface of the enamel as a protective structure called what?

Answer 14

reduced enamel epithelium

Question 15

the undifferentiated cells (stem cells) of the dental papilla become what three things? and what does the dental papilla ultimately become?

Answer 15

• -odontoblasts
• -fibroblasts
• -reserve cells

-pulp tissue

Question 16

the undifferentiated cells (stem cells) of the dental follicle become what 4 things? and what does the dental follicle ultimately become?

Answer 16

• -cementoblasts
• -fibroblasts
• -osteoblasts
• -reserve cells

-periodontal ligament

Question 17

the enamel organ is attached to both mesenchymal parts of the tooth germ by a ___ ___

Answer 17

basal lamina

Question 18

when does the reduced enamel epithelium stop protecting the enamel?

Answer 18

when the tooth enters the oral cavity

Question 19

the outer and inner layers of the enamel organ come together, at the cervical loop, forming a double epithelial layer called what? and what 2 main functions does it have?

Answer 19

hertwig’s epithelial root sheath

• -determines root dentin outline
• -determines # of root canals of teeth